Spark-plug for internal-combustion engines.



W. H. GRAINGER.

SPARK PLUG FOR INTERNAL COMBUSTION ENGINES. APPLICATION FILED our. 22,1914.

14,264,870. Patented Apr. 30, 1918.

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WILLIAM H. GRAINGER, OF TRENTON, NEW JERSEY.

SPARK-PLUG FOR INTERNAL-COMBUSTION ENGINES.

Specification of Letters Patent.

Patented Apr. 30, 1918.

Application filed October 22, 1914. Serial No. 867,980.

To all whom it may concern:

Be it known that I, WILLIAM H. GRAIN- GER, a citizen of the UnitedStates, and a resident of Trenton, in the county of Mercer and State ofNew Jersey, have inventedcertain new and useful Improvements in SparkPlugs for Internal-Combustion Engines, of which the following is aspecification.

The invention relates to improvements in electric ignition devices,commonly called spark plugs, for internal combustion engines, and itconsists in the novel features, structure and combinations of partshereinafter described, and particularly pointed out in the claims.

The object of the invention is, generally speaking, to provide a sparkplug which may be conveniently manufactured and composed of a limitednumber of parts and in operation be highly efiicient and reliable, andmore specifically the object of the invention is to provide a spark plugcomprising a main exterior casing carrying one electrode and aninsulating core or body carrying the other electrode, said exteriorcasing being adapted to be screwed into a wall of the engine cylinderand said insulating core or body being secured Within said exteriorcasing by suitable cement thoroughly hardened, as by baking, andengaging undercut surfaces or grooves or threads formed on the exteriorof said core or body and the ad acent interior surfaces of said exteriorcasing.

A further object of my invention is to dispense with the usual bushingwhich is employed to hold the porcelain of a spark plug in position andto dispense with the customary packing employed for forming tight jointsbetween said bushing and the insulating or porcelain body as well as thepacking which is commonly employed between said body and the exteriorcasing, the entire construction of the spark plug being thus simplifiedand at the same time rendered more efiicient and less liable to becomeinjured or have its correct operation impaired.

The spark plug of my invention comprises two main parts, one being theexterior casing carrying one electrode and the other the insulating coreor body carrying the other electrode and permanently secured within theexterior casing by means which, while securing the two parts together,form a gastight joint between said parts.

The invention will be fully understood from the detailed descriptionhereinafter presented, reference being had to the accompanying drawings,in which:

Figure l is a side elevation of a spark plug embodying my invention;

Fig. 2 is a central vertical section through the same, and

Fig. 3 is a side elevation of the insulating core or body detached fromthe plug.

In the drawings 10 designates the exterior casing or shell carrying oneelectrode 11 and receiving an insulating core or body 12 carrying theother electrode which I number 13. The casing or shell 10 issubstantially of known form and construction, being screw-threaded toenter a threaded opening in the wall of a cylinder and having apolygonal portion to receive a wrench. The casing or shell 10 is ofmetal, as usual. lVithin the casing or shell 10 is formed, at the lowerportion thereof, a cylindrical chamber 14 and at the upper portionthereof a larger cylindrical chamber 15, said chambers merging into eachother and at their point of juncture creating a seat for the insulatingcore or body 12. The wall of the upper chamber 15 is roughened, and inthe present instance this roughness is created by the formation of ascrew-thread 17 in said wall.

The insulating body or core 12 is of elongated form and at its upperportion is formed with a part or head 18 of larger diameter than thelower part of said core or body, the presence of said head 18 creatingat the lower end thereof an annular shoulder 19 adapted to bear upon theupper edges of the exterior casing 10, as shown in Fig. 2. Below theshoulder 19 the core or body 12 is preferably formed with annulargrooves 20, and this portion of the core or body 12 is less in diameterthan the diameter of the chamber 15, whereby a substantial space is leftbetween the wall of said chamber and the adjacent surface of said coreor body, and into this space is filled the cement or holding substance21, which entirely fills said space and also the grooves 20 and thethreads 17 and in addition extends downwardly upon the upper surface ofthe annular shoulder 16 which forms a lower seat for the core or body12, as shown in F i 2.

The core or body 12 is formed ad acent to the shoulder 16 on the shell10 with an annular shoulder 22 to cooperate with said shoulder 16 inproperly sustaining the core or body in position, and below saidshoulder 22 the core or body 12 is of reduced diameter and extendsdownwardly into the chamber 14 of the casing 10 without projectingentirely through said casing. The lower por tion of the core or body 12is formed with a chamber, as usual, through which the electrode 13extends and which chamber cooperates with a chamber surrounding thelower portion of the core or body 12 to avoid the deposit of carbonwithin the plug. At its upper end the core or body 12 is formed with acentral recess 23 which is in communication with a central longitudinalopening 24 within the core or body to receive the electrode 13. Withinthe recess 23 is a plug 24 whose outer surface is serrated, as at 26,and which plug is formed integrally with an annular shoulder or disk 27and outwardly projecting threaded atom or screw 28, said screw or stem28 coin provided to receive the binding iu't by which a conductorterminal may be held against the annular shoulder or dis The upper endof the electrode 13 is secured within the plug 25 and said plug andelectrode are secured within the core or body 12 by a cementing orholding substance 30 which surrounds the plug 25 within the recess 23and that portion of the electrode 13 which is within the hole or opening24. The plug 25 is serrated vertically on its surface so as to aid inresisting any tendency for said plug to turn during the tightening ofthe nut 29, the cementing or holding material 30 entering into firmrelation with the serrations in said plug and the inner walls of therecess 23 and central opening or hole 24 for the electrode 13 and alsoclosely binding against the said electrode. The core or body 12 willhave a glazed exterior surface except on that portion thereof which isbetween the shoulder 19 and shoulder 22 and at this part of the core orbody the exterior surface thereof will be left unglazed, as shown inFig. 3, whereby a somewhat roughened surface is produced with which thecementing or holding substance 21 may enter into interlocking relation.

One of the main features of my invention resides in the provision of theinsulating body or core 12 and exterior casing 10 and securing saidparts together by the holding or cementing material 21, the usualbushings and packings being entirely dispensed with, and in carrying outthis feature of my invention I prefer to construct the adjacent surfacesof the core or body 12 and exterior casing 20 in the manner hereinbeforedescribed, the core or body 12 being of porcelain and the shell 10 ofmetal, and secure these two parts together by holding or cementingmaterial 21 applied upon the core or body 12 in such quantity as tocompletely fill the chamber 15 when said core or body is pushed firmlyinto position in the outer portion of the casing 10 and then baked onder a high degree of heat in order to make the same very hard and ofsuflicient strength and of proper character to key the body or core 12within the casing 10 and effect the permanent connection of said partsas well as to create a hermetically sealed joint between them. 1preferably use a cementing substance containing porcelain, and in thebaking of this substance it becomes very hard and finally enters intosuch close binding relation to the core or body 12 and shell 10 as to bein effect, if not in reality, substantially an integral part thereof. Itwill be seen on reference to Fig. 2 that the holding or cementingsubstance 21 when hardened will key the core or body 12 within the shell10 and prevent the withdrawal of said core or body from said shell. I donot limit this invention to the presence of the two annular grooves 20in the core or body 12, since a highly efficient spark plug would beproduced if the core or body 12 had only one of the annular grooves 20or other undercut surface enabling the cementing or holding substance 21to key the body or core 12 firmly in position within the casing 10.

I do not limit this invention to the securing of the electrode 13 bymeans of the plug 25, since this plug entering a recess in the outer endof a porcelain or insulating core or body and holding an electrode isnot my invention and is to be made the subject of a separate applicationfor Letters Patent so that the same may be protected. My inventionresides more largely in the construction of the spark plug of two mainparts, to-wit, the shell 10 and insulating core or body 12 keyed orfirmly secured together by cementitious material, bushings, gaskets andthe like being dispensed with.

What I claim as my invention and desire to secure by Letters Patent, is:

1. In a spark plug, in combination, a main casing carrying oneelectrode, an insulating core therein carrying the other electrode, andcementitious material keying said casing and core permanently together,said casing in its surface opposite to said core at which thecementitious material is applied being threaded and said core at saidlocation being undercut whereby the cementitious material engagesundercut surfaces of both said core and casing for aiding in the lockingof the two parts together byimeans of said material, and said casingforming therein a commodious chamber for the inner end portion of saidcore and separated at its walls therefrom and said core terminating atits inner end within said chamber and at its outer portion extendingbeyond said caslng.

2. In a spark plug,in combination, a main casing having an enlargedchamber in its outer portion and a shoulder at the base thereof andcarrying one electrode, an insulating core carrying the other electrodeand inserted Within said casing and having a head to engage the outerend thereof and a shoulder to seat on the said shoulder of said casing,and cementitious material applied Within said chamber and keying thecasing and core permanently together, said plug at the location of saidcementitious material having undercut surfaces to receive said materialand thereby aid in locking the said main parts together, and said casingforming therein a commodious chamber for the inner end portion of saidcore and separated at its Walls therefrom and said core terminating atits inner end Within said chamber and at its outer portion extendingbeyond said casing.

Signed at Trenton, in the county of Mercer and State of New Jersey, this20th day of October A. D. 1914.

WILLIAM H. GRAINGER.

Witnesses:

ALFRED C. GRAINGER, E. R. CARROLL.

Copier 0! this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. 0.

